Enkephalin, methionine

In the anterior pituitary gland (see Hormones, anteriorpituitaryhormones), both adrenocorticotropic hormones (ACTH) and the endogenous opiate hormone, P-endorphin, are synthesized from a common prohormone (2) (see Opioids,endogenous). In the adrenal medulla, five to seven copies of another opiate hormone, methionine—enkephalin (Met-enkephalin), and one copy of leucine—enkephalin (Leu-enkephalin) are synthesized from each precursor molecule (3). 

What is the amino acid sequence (using three-letter abbrevia- tions) of methionine enkephalin Also show it using one-letter abbreviations. I... 

Delta receptors are relatively selective for two related penta-peptides, methionine enkephalin and leucine enkephalin (met- and leu-enkephalin), which were isolated from porcine brain (Hughes 1975). Both met- and leu-enkephalin inhibit electrically induced contractions of guinea pig ileum, an effect that mimics those effects seen with opioid drugs, and is naloxone reversible. The enkephalins are processed posttranslational ly from proenkephalin, and secreted from central and peripheral neurons and endocrine cells in the adrenal medulla. 

Gintzler AR, Xu H. Different G proteins mediate the opioid inhibition or enhancement of evoked methionine] enkephalin release. Proc Natl Acad Sci USA 1991 88 4741-4745. 

Wybran, J. et al., Suggestive evidence for receptors for morphine and methionine enkephalin on normal human blood T-lymphocytes, J. Immunol., 123, 1068, 1979. 

Hong, J. S., Yang, H.-Y. T., Fratta, W., and Costa, E. (1978) Rat striatal methionine-enkephalin content after chronic treatment with cataleptogenic and non-cataleptogenic antischizophrenic drugs. J. Pharmacol. Exp. Ther., 205 141-147. 

Nabeshima, T., Hiramatsu, M., Amano, M., Furukawa, H., and Kameyama, T. (1983) Decrease of methionine-enkephalin levels in mouse brain induced by phencyclidine. Eur. J. Pharmacol., 86 271-273. 

Y Okada, N Ohta. Amino acids and peptides. VII. Synthesis of methionine-enkephalin using transfer hydrogenation, (cyclohexene) Chem Pharm Bull (Jpn) 30, 581, 1982. 

Chun IK, Chien YW (1993) Transmucosal delivery of methionine enkephalin. I Solution stability and kinetics of degradation in various rabbit mucosa extracts. J Pharm Sci 82 373-378. 

The spin-spin coupling constants [2-4] of the enkephalins in solution can be interpreted in terms of folded conformations resembling that of morphine in the placement of the residues which appear important for biological activity. X-ray crystallography and theoretical calculations (4-9) have also shown that methionine and leucine enkephalin adopt conformations similar to those concluded from NMR studies. Hence it would appear that opioid peptides can topographically resemble the opiates by assuming preferred, folded, conformations. However, earlier studies from this laboratory (TO) have shown that NMR data can be interpreted in terms of a conformationally flexible structure for methionine enkephalin. 

Figure 2. C-13 chemical shifts of the glycyl residues in [2-[2-C-13]glycine]me-thionine enkephalin and [3-[2-C-13]glycine]methionine enkephalin in the presence of 75.0 and 78.5 mg of PS, respectively, as a function of pH, 30°C. Shifts observed for enkephalin in the absence of PS (see Figure 3), (-------...

Figure 3. C-13 chemical shifts of the glycyl-2 and glycyl-3 residues of methionine enkephalin as a function of pH, 30°C...

Table I. Linewidths of [2-[2- C] glycine] and [3-[2- C] glycine]Methionine Enkephalin in the Presence of PS at Various "pH "s...

Figure 3. The pH dependence of Ti of [3-[2-C-13]glycine]methionine enkephalin (1.1 mg) in presence of phosphatidyl serine (78.5 mg). Spectra were run at...

Rotational correlation times obtained from the observed C Ti values of the glycyl residues in methionine enkephalin as a function of "pH" are given in Figure 6. The 3-glycyl residue... 

Figure 6. Plot of correlation times corresponding to observed T, values of [2-[2-C-13]glycine]methionine enkephalin (X) and of [3-f2-C-13]glycine]methio-nine enkephalin (O) in presence of PS as a function of pH (1.1 mg of peptide in the presence of ca. 75 mg PS), 30°C...

C]glycine] methionine enkephalin by varying the lipid concentration in the presence of a 1.2 mg/ml sample of enkephalin Figures 7 and 8 represent plots of(Ti p/T p-Tj... 

Using the g obtained above and the pH-dependence of the Tj measured for [2-[2- C]glycine] methionine enkephalin (see... 

It is informative to compare the observed dissociation constant for the enkephalin-PS interaction with those reported for other systems. Methionine enkephalin has been shown ( ) to bind to brain membrane with a high affinity binding constant of 1.7 X IQ M and a low affinity binding constant of 1.7 x 10 ... 

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